Characteristics of a nanocluster change remarkably even when the number of its constituent atoms increases or decreases by one. Therefore, development of technique for generating a nanocluster beam with controlled distribution of the number of constituent atoms of the nanocluster (hereinafter, referred to as cluster size) has been a challenge to be addressed.
Development of nanocluster sources using a magnetron sputtering method operated by a direct-current power supply (hereinafter, referred to as DC-MSP method) has lent some improvement to the efforts to the above challenge. For instance, Non-patent document 1 suggests a possibility that the cluster size can be controlled by mainly controlling helium (He) partial pressure (refer to FIG. 4 of Non-patent document 1). Non-patent document 2 describes an influence of the shape of a He gas nozzle on the cluster size (refer to FIG. 4 of Non-patent document 2).
However, solutions are still required for a challenge that the amount of the generated nanoclusters is small because the control of the size distribution is difficult and the intensity of the nanocluster ion beams after selection of cluster size is equal to or lower than several tens pA (0.6 to 3×108 particles per second), which is weak.
In addition, Patent documents 1 to 3 and Non-patent documents 3 to 5 should be referred to as related literatures.